Retired general James Mattis once led U.S. Central Command. / Alex Brandon, AP

by Tom Vanden Brook and Jim Michaels, USA TODAY

by Tom Vanden Brook and Jim Michaels, USA TODAY

WASHINGTON - Taxpayers and troops will receive something of a peace dividend under White House plans to withdraw troops from Afghanistan by the end of 2016.

The new strategy reflects Americans' weariness of war.

"The bigger backdrop is that the public does not support large troop deployments in Afghanistan or elsewhere," said Gordon Adams, a former Pentagon budget official who teaches at American University. "This means budget attention has shifted to jobs, immigration, health, deficits and less on defense."

But James Mattis, a retired Marine four-star general who led U.S. Central Command, which oversaw the wars in Iraq and Afghanistan, said announcing a lower U.S. troop number and setting a specific withdrawal date "sends a message" to U.S. allies that it is not fully committed to the fight against the Taliban.

"Why does the U.S. government have to level the playing field for the enemy?" Mattis said.

The White House estimates the cost of keeping about 10,000 troops and supporting the Afghan security forces to be about $20 billion in fiscal year 2015. That's about what it cost to fight there in 2005, and nearly $100 billion less than peak spending in 2011. Deployments, which peaked in 2007 with 15-month tours for soldiers in Iraq and Afghanistan, will be far fewer and further between.

Presumably, those savings could be used elsewhere. President Obama proposed, for example, a new fund of up to $5 billion to help allies fight terrorists during his foreign policy address Wednesday at the U.S. Military Academy at West Point. It might also be used to help fund the military's shift of resources to Asia and to fight terrorists in other places such as Africa.

A significant aspect of the $20 billion figure for Afghanistan is that it doesn't appear padded to include costs not associated with the war, said Todd Harrison, a military spending expert at the non-partisan Center for Strategic and Budgetary Assessments. Last year, the Pentagon shifted about $30 billion in spending from its regular budget to the special war-time bill of $80 billion for Afghanistan, he said.

That allowed the Pentagon to stay below the cap set by congressional negotiators, Harrison said.

The Pentagon and the president, as they did last year, are likely to get most anything they want, Adams said. Democrats are eager to back their president and the military; Republicans want to appear as supportive or more so.

"The money is always there," Adams said.

The military initially requested that a larger number of troops remain behind in Afghanistan after the combat mission ended at the end of this year.

"We asked for 13,600 troops several years ago," Mattis said.

"We want to crush the enemy's hope to win through violence," Mattis said. "Yet we have now given the enemy hope that if they hang on until our announced withdrawal date they can perhaps come back."